The conventional tape cassette of this sort for a video tape recorder is constituted as shown in FIGS. 1 to 3.
Firstly, as illustrated in FIG. 1, a cassette housing 3 having an upper half 1 and a lower half 2, a front cover 4 and a rear cover 5 are made of synthetic resin. A magnetic tape 8 is wound around a pair of right and left reels 6 and 7 and accommodated in the upper and lower haves 1 and 2. These halves 1 and 2 are fitted in each other and joined by a pair of screws (not shown) to form the cassette housing 3.
Disposed in the fore part of the cassette housing 3 is a front opening 10 which extends in the right to left direction over the total length of the cassette housing 3. A pair of tape guides 11 are provided within the cassette housing 3 near the respective right and left ends of the front opening 10 and formed integrally with this cassette housing 3. The magnetic tape 8 is guided by this pair of tape guides 11 and passed along the front opening 10 as shown in FIG. 2.
The cassette housing 3 has a U-shaped recess formed between the pair of tape guides 11 and inwardly of the front opening 10. This recess 12 is separated from a portion of the cassette housing 3 where the reels 6 and 7 are accommodated by a U-shaped partition wall 13 formed integrally with the cassette housing 3, and opened at its top and bottom sides.
The front cover 4 is almost of U-shape and has integrally a pair of pivots 15 projected inwardly from their respective right and left end portions 4a thereof and aligned with each other. And as shown in FIG. 2, the pair of pivots 15 are respectively inserted in a pair of insertion holes 16 which are formed in the fore parts of the right and left side walls 3a of the cassette housing 3 and the axes of which are aligned with each other, so that the front cover 4 can be swung on the pivots 15 so as to cover the front side of the magnetic tape 8 passed along the front opening 10.
The rear cover 5 has integrally a top cover 17 on its upper edge as shown in FIG. 1 and a pair of pivots 18 which are so located almost at the centers of their right and left ends in the vertical direction thereof as to be aligned with each other. And as shown in FIG. 2, the rear cover 5 is arranged in parallel with the front cover 4 within the recess 12 so as to cover the rear side of the magnetic tape 8 passed along the front opening 10.
The pair of pivots 18 are inserted in respective insertion holes 20 provided in a pair of projecting pieces 19, which are so formed integrally with the front cover 4 and near the right and left end poritons 4a of the front cover 4 as to project from the back of the front cover 4 as shown in FIGS. 1 and 2, so that the rear cover 5 can be rotated on the pivots 18. The top cover 17 is arranged to cover the recess 12 in as illustrated in FIG. 2.
The right and left end portions 13a of the partition wall 13 are opposed to each other as shown in FIGS. 1 and 2. Disposed on the opposed faces of the right and left end portions 13a are a pair of guide grooves 21 which are of gentle S-shapes and opened at their upper ends.
A pair of projecting pieces 22 are projected backwardly from the respective right and left ends of the rear cover 5 below the pivots 18 and a pair of guided pins 23 are so projected outwardly from the respective projecting pieces 22 as to be aligned with each other and fitted loosely in the respective guide grooves 21. Further, the front cover 4 is urged to rotate in direction of arrow a in FIG. 2, i.e. in its closed direction by a torsion spring (not shown), and locked by a lock lever, when closed.
When the above-mentioned tape cassette is not in use, the front cover 4 is closed and locked as indicated in solid lines in FIG. 2, and in this state, the magnetic tape 8 passed along the front opening 10 is enclosed by the front and rear covers 4 and 5, in other words, the tape cassette is in a state of being completely closed.
When the tape cassette is loaded into the video tape recorder, the front cover is unlocked and turned by an angle of about 90.degree. in direction of arrow a', i.e. in its opened direction to open the front opening 10. And when the front cover 4 is so turned on the pivot 15 from its closed position indicated in solid lines to its opened position indicated in phantom lines in FIG. 2, the pivot 18 of the rear cover 5 is also removed to the position indicated in a phantom line in FIG. 2 together with this front cover 4, so that the rear cover 5 is moved to its opened position indicated in phantom lines in FIG. 2 with the front cover 4.
During this movement of the rear cover 5, the guided pins 23 are guided by the respective guide grooves 21 and moved in direction of arrow c, so that the lower end portion 5a of the rear cover 5 is swung on the pivots 18 backwardly away from the front cover 4 in direction of arrow d. On the contrary, when the front cover 4 is rotated in direction of arrow a in FIG. 2 to be closed, the rear cover 5 is moved in the same direction as the front cover 4, with rotation in direction of arrow d' as the guided pin 23 is moved in direction of arrow c' within the guide groove 21, so that the lower end portion 5a of the rear cover 5 returns to the original position as indicated in solid lines in FIG. 2.
However, in such a tape cassette constituted and functioning as mentioned above, there is a fault as described below.
That is, the feature of the tape cassette of this sort is that the magnetic tape 8 passed along the front opening 10 of the cassette housing 3 is completely enclosed by the front and rear covers 4 and 5, when the front cover 4 is closed. Therefore, the lower end portion 5a of the rear cover 5 is at first lowered in direction of arrow e passing near the back side of the magnetic tape 8 as shown in FIG. 3, and then moved around below the magnetic tape 8 in direction of arrow f to be brought to the position indicated in phantom-lines in FIG. 3, where the lower end portion 5a of the rear cover 5 abuts on its front surface 25 against a notched portion 26 provided at the lower back surface 4b of the front cover 4.
In the state above-mentioned, the front surface 25 of the rear cover 5 extends vertically in parallel with the lower back surface 4b of the front cover 4. Therefore, as indicated in solid lines in FIG. 3, among all the portions of rear cover 5 the upper corner portion 27 of the front surface 25 approaches nearest to the magnetic tape 8, as the rear cover 5 is closed, so that the distance l.sub.1 between the upper corner portion 27 of the front surface 25 and magnetic tape 8 becomes very small.
Hence, it is necessary to make the above distance l.sub.1 large to a certain degree, so as to prevent the magnetic tape 8 from coming in contact with the upper corner portion 27 or from being caught between the covers 4 and 5, while the rear cover is closed. From this reason, it is standardized that the distance l.sub.1 of the tape cassette of this sort is to be more than 1 mm.
However, the cassette housing 3, front cover 4 and rear cover 5, etc. are made of synthetic resin, so that their dimentional errors due to molding are not avoidable. Therefore, it is difficult to hold the distance l.sub.1 always within a predetermined extent. As a result, it often occurs that the upper corner portion 27 comes in contact with the magentic tape 8, or that the magnetic tape 8 is caught between the covers 4 and 5. Doubtlessly, it becomes a glaring fault for the tape cassette of this sort.